1. Field
The following description relates generally to wireless communications, and more particularly to facilitating acknowledgment and retransmission of wireless data in a wireless communication system.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content, such as voice content, data content, and so on. Typical wireless communication systems can be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, . . . ). Examples of such multiple-access systems can include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and the like. Additionally, the systems can conform to specifications such as third generation partnership project (3GPP), 3GPP long term evolution (LTE), ultra mobile broadband (UMB), or multi-carrier wireless specifications such as evolution data optimized (EV-DO), one or more revisions thereof, etc.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple mobile devices. Each mobile device can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations. Further, communications between mobile devices and base stations can be established via single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, multiple-input multiple-output (MIMO) systems, and so forth.
For wireless communication in general, signal timing is an important aspect of successful transmission and reception of data. Wireless signals are generally divided in time into multiple time frames, comprising multiple time subframes. In some wireless systems, time frames can be designated for uplink (UL) transmission or downlink (DL) transmission. Alternatively, or in addition, various frequency bands or code spreads can be designated for UL transmission or DL transmission as well. This provides an overt mechanism to distinguish UL and DL transmission sequences, whether by turn-based time subframes, or by orthogonal frequency bands or code spreads, to mitigate interference. Furthermore, accurate timing is an important part of successfully demapping and demodulating a wireless signal; without knowing what symbols to expect at a particular time, proper wireless reception can be difficult or impossible, depending on circumstances.
Another common aspect of wireless communication is acknowledgment and retransmission protocols between wireless receivers and wireless transmitters, respectively. Acknowledgment involves a receiver conveying to a transmitter that particular data packets have been received successfully, or that particular packets have not been received successfully. In turn, the transmitter can then retransmit packets lost by the receiver, or proceed to another sequence of transmissions if a previous sequence is successfully received at the receiver. In this manner the transmitter and receiver can reliably exchange information, even in adverse wireless conditions (e.g., with high packet loss).
Although explicit acknowledgment of received and lost data can provide highly reliable wireless data exchange, competing aspects of wireless communication exist that limit full explicit acknowledgments. For instance, to maximize wireless resources and bandwidth, protocol schemes are often derived to approximate various wireless communication functions at lower bandwidth cost. Acknowledgment and retransmission is no exception to this concept. Accordingly, many acknowledgment and retransmission protocols do not explicitly identify all lost packets, but rather employ coding protocols that can be utilized to infer identity of lost packets, with minimal wireless resources. Although generally effective, these coding protocols can lead to errors, duplicate transmission of data packets, or failed retransmission of lost packets. Thus, one aspect of existing protocol engineering is minimizing these errors without significantly impacting radio link control bandwidth.